1. Field of the Invention
The present invention relates to a radio telecommunication apparatus.
2. Description of the Related Art
Since automobile telephone apparatuses are used while driving, they are often designed to perform speech communication not only by a handset but also by a handsfree arrangement constituted by a unit microphone and a loudspeaker. Such an arrangement requires a means for allowing a user to control the volume of the loudspeaker.
As such a control means, a combination of push-type volume up and down keys is generally used. These keys are, for example, arranged together in a concentrated manner with numerical keys and function keys, as shown in FIG. 1, so as to improve its operability.
Similar to various types of electronic devices, automobile telephone apparatuses are required to be relatively small in size. A demand for reduction in size is high especially for a so-called portable automobile telephone apparatus, in which a handset serves as a radio telecommunication apparatus independently of a main body, in order to improve its portability. In this case, since the above-mentioned keys are arranged on the handset, they are also required to be decreased in number. In order to satisfy such a demand, some apparatuses are designed such that the above-mentioned volume keys are replaced with one volume key, and in response to depression of the volume keys the volume is changed in only one direction in which the volume is increased or decreased. If, for example, volume changes are set in the direction to increase in response to the push of the key, the volume is increased upon pushing of the key. When the volume reaches the maximum level, it is increased from the minimum level again.
In this case, however, it takes much time to set the volume to a desired level by changing the volume in a direction reverse to a desired direction. In addition, since the volume is greatly changed when it shifts from the maximum level to the minimum level, a problem is posed in terms of operability.